But silent payment will not be transparent as it is not even existing on blockchain at all and the public will know about the transaction. The payment will not be traceable.
If this can be like a layer 2, it will be better, in a way there will be a bridge between silent payment and on-chain transaction just like lightning network.
Apparently, you misunderstood the concept. The silent payment is an on-chain transaction like any other: it exists, is written into the blockchain, and is visible to everyone who has a copy of blockchain data. It doesn't hide the fact of payment: it hides the fact that a certain address in the blockchain was derived from the "silent" address you made public. The sender will know that this new address belongs to the you because he used your data to generate it. The receiver will know this new address belongs to him because he scans the blockchain for all addresses he can spend. Others will not know this new address is yours because they can't know a secret that was used to create this new address. However, others can generate their own addresses by modifying the "silent" address you made public. Each of these transactions will be broadcast to the network and written into the blockchain.